Index: ntoskrnl/fsrtl/filelock.c
===================================================================
--- ntoskrnl/fsrtl/filelock.c	(revision 58218)
+++ ntoskrnl/fsrtl/filelock.c	(working copy)
@@ -9,7 +9,7 @@
 /* INCLUDES ******************************************************************/
 
 #include <ntoskrnl.h>
-#define NDEBUG
+//#define NDEBUG
 #include <debug.h>
 
 /* GLOBALS *******************************************************************/
@@ -858,7 +858,10 @@
     Find.Exclusive.FileLock.StartingByte = *FileOffset;
     Find.Exclusive.FileLock.EndingByte.QuadPart = 
         FileOffset->QuadPart + Length->QuadPart;
-    ASSERT(InternalInfo);
+    if (!InternalInfo) {
+        DPRINT("File not previously locked (ever)\n");
+        return STATUS_RANGE_NOT_LOCKED;
+    }
     Entry = RtlLookupElementGenericTable(&InternalInfo->RangeTable, &Find);
     if (!Entry) {
         DPRINT("Range not locked %wZ\n", &FileObject->FileName);